Fracture Toughness of TiN Coating as a Function of Interlayer Thickness

Abstract

Single layer TiN and Ti/TiN bilayers were deposited on H-13 steel by plasma enhanced chemical vapor deposition technique. TiN thickness was kept constant at 2 μm and Ti thickness values ranged between 100 nm to 1 μm. Fracture toughness and residual stress of TiN coatings was measured as functions of thickness of titanium interlayer. Vickers indentation tests, X-ray diffraction, optical microscopy and field emission scanning electron microscopy were used to characterize the coatings. Results showed fracture toughness of the coating increases severely by increasing interlayer thickness. Additionally, internal stress which causes debonding and breaking of the entire coating, reduces about 70% by increasing interlayer thickness up to 600 nm. Moreover, there is maximum value for interlayer thickness in order to optimize fracture toughness of the coating.